1. Field of the Invention
The present invention concerns formation of a wiring film in a production process of semiconductors typically represented by ULSI and, more in particular, it relates to a method of forming a film of a wiring material of copper or copper alloy by a electrolytic plating method and, further, heat treating the film in a high pressure/high temperature gas atmosphere thereby filling the holes in a connection portion or wiring trenches with a material for the wiring film and obtaining good adhesion.
2. Related Art Statement
Japanese Patent No. 2660040 (registered on Jun. 6, 1997) discloses "a vacuum film forming method comprising a step of forming a thin metal film on a substrate having concave portions by a vacuum thin film forming method such as a sputtering method, CVD process or vacuum vapor deposition process, a step of heating and fluidizing the entire thin metal film formed on the substrate and a step of pressurizing the metal of the fluidized thin metal film with a gas and filling the metal of the thin metal film into the concave portions so as not to form voids in the concave portion".
Further, Japanese Patent Publication No. Hei 7-193063 discloses a method of treating an article having a surface and having at least one concave portion within the surface, the method includes forming a layer on at least a portion of the surface, the layer extending over the concave portion and, further, exposing the article and the layer to high pressure and high temperature enough to deform a portion of the layer so as to fill the concave portion".
This prior publication describes that the article is a semiconductor wafer and the concave portion comprises, for example, holes, trenches and viaholes formed to the semiconductor wafer and the layer is made of a metal such as aluminum.
Further, it also discloses that, in a case where the layer is made of aluminum, the temperature is from 350 to 650.degree. C. and the pressure is at 3,000 psi or higher, a gas can also be used for pressurization and it is necessary that the layer formed over the hole or the groove has a thickness at least equal with the width of the hole.
Further, it describes that even when a semiconductor wafer itself includes a plurality of layers of different characteristics, it can be produced as a result of a production process including a plurality of steps for forming them.
As described above, the known prior arts disclose that squeezing or introducing the material by high pressure at a high temperature is effective as a method of filling voids formed in the holes or trenches for improvement of the electro-conductivity of the wiring film (mainly) of semiconductors.
However, the Al wiring films shown by the prior literatures have come to their limit in view of the electron migration (EM) resistance or lowering of electric resistance required along with finer/higher integration of ULSI in the feature. While Cu has been expected recently as being excellent over Al with respect to the situations described above, since the conditions for film formation and the film structure after film formation of Cu greatly differ from those of Al and no comparable effect can be obtained if the prior art described above is applied as it is.
Particularly, with respect to the copper wiring film, since it is difficult for line fabrication by etching after forming the wiring film by the PVD method as in the Al wiring film, a method of previously forming trenches in the insulation film, in which the material for the copper wiring film is filled and then scraping off by grinding to form wirings has been adopted. Further, in this case, an electrolytic plating method is considered advantageous in view of the cost and the productivity and many semiconductor manufacturers have earnestly intended for the establishment of the technique. Further, the electrolytic plating method has advantages that the electrolytic plating is a low temperature process carried out near the room temperature and enables combination with an organic series material having a heat resistance at 350 to 380.degree. C. and considered as a promising candidate with regard to the subject of lowering the dielectric constant of the insulation film material, which is considered important along with temperature lowering of the wiring film material.
The present inventors have made a study based on experiments or the like by applying such prior art to copper series wiring films, particularly, copper wiring films formed by electrolytic plating method, found several problems and have reached the present invention.